1. Technical Field
The present invention relates to a multilayer structure forming method using a droplet discharge apparatus, and in particular, to a multilayer structure forming method which is suitable for manufacturing of a wiring board and manufacturing of an electronic apparatus.
2. Related Art
In recent years, attention has been paid to a method of manufacturing wiring boards or circuit boards using an additive process by a printing method. This is because the cost of the additive process is low as compared with a method of manufacturing wiring boards or circuit boards by repeatedly carrying out a process of coating a thin film and a photolithographic process.
As one of the techniques that are utilized in such an additive process, a technique of forming conductive patterns using an inkjet method has been known (for example, JP-A-2004-6578).
When a wiring pattern is formed by the inkjet method, a pattern of a conductive material disposed by a droplet discharge apparatus is baked to obtain a wiring pattern. The surface of the wiring pattern formed by baking has a lyophobic property against a liquid insulating material, such as acrylic resin. Therefore, it is not difficult to draw insulating patterns defining the outer shape of via holes on such a wiring pattern, by the inkjet method.
However, the baking at the time of baking the wiring pattern causes surfaces even other than the wiring pattern to exhibit a lyophobic property. Specifically, the baking makes the surface of an insulating layer, which is exposed at another portion than the wiring pattern, lyophobic. Therefore, it is difficult to laminate insulating layers with uniform thickness in other portions than the vicinities of via holes by the inkjet method.
Further, when an insulating layer having via holes or contact holes is formed by the inkjet method, it is required to use a liquid material having a relatively high concentration. This is because the time required until the liquid material having a relatively high concentration loses its fluidity due to vaporization of a solvent after being discharged is so short that the outer shape of openings becoming the via holes can be easily shaped.
However, the area that such a liquid material spreads on a surface of an object after landing is small. Therefore, such a liquid material is suitable for forming portions bordering via holes in an insulating layer, but it causes difficulties in forming portions away from the via holes.